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  2. Coherence (physics) - Wikipedia

    en.wikipedia.org/wiki/Coherence_(physics)

    Temporal coherence is the measure of the average correlation between the value of a wave and itself delayed by , at any pair of times. Temporal coherence tells us how monochromatic a source is. In other words, it characterizes how well a wave can interfere with itself at a different time.

  3. Horn antenna - Wikipedia

    en.wikipedia.org/wiki/Horn_antenna

    The reflected waves cause standing waves in the waveguide, increasing the SWR, wasting energy and possibly overheating the transmitter. In addition, the small aperture of the waveguide (less than one wavelength) causes significant diffraction of the waves issuing from it, resulting in a wide radiation pattern without much directivity.

  4. Doppler effect - Wikipedia

    en.wikipedia.org/wiki/Doppler_effect

    The Doppler effect (also Doppler shift) is the change in the frequency of a wave in relation to an observer who is moving relative to the source of the wave. [1][2][3] The Doppler effect is named after the physicist Christian Doppler, who described the phenomenon in 1842. A common example of Doppler shift is the change of pitch heard when a ...

  5. White light interferometry - Wikipedia

    en.wikipedia.org/wiki/White_light_interferometry

    The interference occurs for white light when the path lengths of the measurement beam and the reference beam are nearly matched. By scanning (changing) the measurement beam path length relative to the reference beam, a correlogram is generated at each pixel. The width of the resulting correlogram is the coherence length, which depends strongly ...

  6. Wavelength - Wikipedia

    en.wikipedia.org/wiki/Wavelength

    The wavelength of a sine wave, λ, can be measured between any two points with the same phase, such as between crests (on top), or troughs (on bottom), or corresponding zero crossings as shown. In physics and mathematics , wavelength or spatial period of a wave or periodic function is the distance over which the wave's shape repeats.

  7. Electromagnetic spectrum - Wikipedia

    en.wikipedia.org/wiki/Electromagnetic_spectrum

    Electromagnetic spectrum. The electromagnetic spectrum is the full range of electromagnetic radiation, organized by frequency or wavelength. The spectrum is divided into separate bands, with different names for the electromagnetic waves within each band. From low to high frequency these are: radio waves, microwaves, infrared, visible light ...

  8. Yagi–Uda antenna - Wikipedia

    en.wikipedia.org/wiki/Yagi–Uda_antenna

    There is a tradeoff between gain and bandwidth, with the bandwidth narrowing as more elements are used. [4] For applications that require wider bandwidths, such as terrestrial television , Yagi–Uda antennas commonly feature trigonal reflectors, and larger diameter conductors, in order to cover the relevant portions of the VHF and UHF bands ...

  9. Terahertz radiation - Wikipedia

    en.wikipedia.org/wiki/Terahertz_radiation

    One terahertz is 10 12 Hz or 1,000 GHz. Wavelengths of radiation in the terahertz band correspondingly range from 1 mm to 0.1 mm = 100 μm. Because terahertz radiation begins at a wavelength of around 1 millimeter and proceeds into shorter wavelengths, it is sometimes known as the submillimeter band, and its radiation as submillimeter waves ...